A wide variety of biofilm carriers, also called biofilm support media or biofilm growth media, are currently being used in water and wastewater treatment processes. The existing biofilm carriers are made of inert (non-carbon based) materials, often some form of plastic, ceramic, or a number of other man-made polymers. See, for example, U.S. Pat. Nos. 7,189,323 B2; 6,936,446 B2; 6,811,147 B2; 6,726,838 B2; 6,666,436 B1; 6,631,890 B1; 6,383,373 B1; 6,214,619 B2; 6,936,170 B1; 6,156,204; 6,126,829; 5,985,148; 5,779,886; 5,543,039.
U.S. Pat. Nos. 6,277,279 B1 ('279) and 6,551,511 B1 ('511) describe the use of carbon-based material in water treatment, but have several distinct limitations. The '279 patent states that combinations of saturated and unsaturated fatty acids are shaped into pellets, powder, granules, or cakes and added to the wastewater at a rate of between 0.01 and 1.0 pounds per thousand gallons of wastewater. The major limitations of the described material include the durability of the combinations of saturated and unsaturated fatty acids, and the effectiveness of the formed shapes. The described carriers would be ineffective in numerous applications such as in an aerated reactor used in the nitrification of wastewater since they are not durable enough to withstand the process. Further, the shapes specified, pellets, powders, granules, and cakes, inhibit optimum performance of the supported biofilm.
U.S. Pat. No. 6,551,511 B1 describes a fatty acid or a fatty alcohol sphere of a diameter no greater that 100 mm on a carrier of polyvinyl alcohol and polyethylene glycol. The major limitations of the material described are the polyvinyl alcohol and polyethylene glycol support structures and the shape of the products. The polyvinyl alcohol and polyethylene glycol support structures are non-reactive, thus will remain in the treatment tank and will have to be periodically removed. Also, the process relies on the pressure drop due to Bernoulli's principle on the surface of the sphere to create an anaerobic zone for processes such as de-nitrification.
Most biofilm carriers are inert and do not provide a carbon-based food source for the supported biofilm. Carbon-based carriers that have been described are not durable enough to perform in all reactor environments and are inefficiently shaped. A need remains for a carbon-based biofilm that is durable and that is configured to provide a strong base for efficiently supporting biofilms.
All patents, patent applications, provisional patent applications and publications referred to or cited herein, are incorporated by reference in their entirety to the extent they are not inconsistent with the teachings of the specification